The present invention relates to an automatic braking system. It finds particular application in conjunction with controlling how an automatic cruise control system applies service brakes during downhill conditions and will be described with particular reference thereto. It will be appreciated, however, that the invention is also amenable to other applications.
For example, an automatic cruise control (ACC) system, in addition to conventional engine based speed control, typically allows for automated application of the vehicle service brakes to maintain either a constant speed or following distance. When a vehicle is traveling downhill and/or following another vehicle (e.g., a forward vehicle), the ACC system may actively decelerate the vehicle by de-throttling the engine, applying the engine retarder (engine brake), and/or applying the vehicle brakes to maintain the vehicle following distance (to the forward vehicle) and speed. If the forward vehicle accelerates away from the ACC vehicle, the system will attempt to accelerate and maintain a set distance behind the forward vehicle until the set speed is achieved. Prolonged application of the service brake by, for example, the ACC system during a downhill following mode may overwork the service brakes and lead to brake fade. Brake fade is caused by a buildup of heat in the braking surfaces, which may lead to reduced friction against the braking surfaces. In order to avoid brake fade, some ACC systems are designed to disengage when the service brakes become close to a brake fade condition.
The present invention provides a new and improved apparatus and method which addresses the above-referenced problems.